Machine guards

ABSTRACT

A guard for an access area of a machine comprising at least two overlying frames mounted for relative sliding movement between two extreme positions, that is open and closed. Each frame carries a guard panel having an area corresponding to only part of the access area, the arrangement being such that when the frames are in the open position the access area is unobstructed as the guard panels overlie one another, whilst when the frames are in the closed position, the guard panels extend adjacent to each other and obstruct the access area. Preferably, the frames nest within each other and sliding movement is transmitted from the inmost frame to the outmost frame. In a preferred embodiment, three rectangular frames are mounted on a portal frame with each guard panel being rectangular and having an area of approximately one-third of the access area.

United States Patent [191 Jones Mar. 18, 1975 [54] MACHINE GUARDS 2,855,184 10/1958 Moore 256/21 [75] Inventor: William Leslie Jones, Tipton, I

England Primary E.ram1nerDenn1s L. Taylor Attorney, Agent, or Firm-lmirie, Smiley & Linn [73] Assignee: A.H.M. Machines Limited,

Birmingham, England Filed: Aug. 6, 1973 Appl. No.: 385,811

Foreign Application Priority Data Aug. 12, 1972 Great Britain 37697/72 References Cited UNITED STATES PATENTS 888,433 5/1908 Thompson 160/202 899,460 9/1908 McCloud 1,281,006 10/1918 Hobson 160/202 UX 2,154,421 4/1939 Cunningham 160/202 2,207,148 7/1940 Hall 160/202 X [57] ABSTRACT A guard for an access area of a machine comprising at least two overlying frames mounted for relative sliding movement between two extreme positions, that is open and closed. Each frame carries a guard panel having an area corresponding to only part of the access area, the arrangement being such that when the frames are in the open position the access area is unobstructed as the guard panels overlie one another, whilst when the frames are in the closed position, the guard panels extend adjacent to each other and obstruct the access area. Preferably, the frames nest within each other and sliding movement is transmitted from the inmost frame to the outmost frame. In a preferred embodiment, three rectangular frames are mounted on a portal frame with each guard panel being rectangular and having an area of approximately one-third of the access area.

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SPECIFIC DESCRIPTION This invention is concerned with improvements in or relating to machine guards primarily intended to safeguard an operator by obstructing the access to machinery during one or more operational sequences. However, this invention may have other useful applications in machines where a guard is required and this invention is not to be considered as limited to the aforementioned intended use.

It is already known to provide machine guards which comprise a shutter arrangement mounted for vertical or horizontal displacement relative to the machine with which they are used. Usually such shutters comprise a panel which dimensionally corresponds to the area to be obstructed. However, in a machine where a guard for a large area has to be provided, such conventional shutters are inconvenient as when the shutter is open or withdrawn, the panel has to be accommodated in a suitable position. This leads to large, complicated arrangements which waste effective space and are relatively expensive to install and maintain because of their size.

Although it also has been proposed to use foldable grilles or hinged slats instead of panels to provide more compact guards, these are also expensive to install and maintain, are subject to excessive wear with consequential problems, and they tend to be slow in operation.

It is an object of this invention to provide an improved machine guard which is compact, simple to install and of versatile application.

According to this invention we provide a guard for a machine having an access area to be opened or closed by the guard, the guard comprising at least two overlying frames mounted on guide means for sliding movement relative to each other between two extreme positions, that is open and closed positions, drive means for so moving the frames, and each frame carrying a guard panel having an areacorresponding to only a part of the machine access area, the arrangement being such that when the guard is in the open position the frames are disposed so that the guard panels overlie one another and the machine access area is unobstructed, and when the guard is moved to the closed position the frames are slid relative to each other and the guard panels are moved from such overlying positions into a position in which in combination they extend adjacent to each other and obstruct the machine access area.

Conveniently, each frame is of a configuration such that it nests within the adjacent overlying frame. The largest frame is arranged so that during the relative sliding movement the necessary amount of movement to clear the guard panel from the machine access area is minimal, and preferably only corresponds to the length (in the direction of movement) of the guard panel.

Similarly, the smallest frame is arranged for maximum movement within the ends of the other frame or frames and any intermediate frames are appropriately and proportionately moved.

Accordingly, as the invented machine guard has overlying frames, the area or space required to be occupied by the frames when the guard is in the open position merely corresponds to the length of movement of the largest frame and this is only a part of the total access area length (in the direction of movement). This means that a particularly compact and simple arrange ment may be achieved.

Preferably, the machine guard includes three frames each carrying a guard panel of the same size and corresponding to one third of the machine access area. However, other arrangements may be devised.

The frames are preferably arranged for vertical displacement and the guide means comprises opposed side rails on which the respective sides of the frames are mounted. It is envisaged that the frames may be arranged for horizontal displacement by providing hori-.

zontal guide rails or tracks.

The driving means may be provided by a counterweight system manually operated, or by an electrical system. However, it is preferred that the driving means is constituted by a pneumatic cylinder connected to one or more of the frames.

Preferably, the pneumatic cylinder is arranged to hold the guard in the open position so that if there should be a failure in the pneumatic supply, the guard returns to the closed position.

When the frames are driven by any form of power operated*mechanism, such as would normally be em- 'ployed when the machine guard is used with an automatic or semi-automatic machine, a safety leading edge device is incorporated in the-driving means. By this means the driving may be interrupted if the leading edge of one of the frames or the panels meets some form of obstruction during closing movement. In all cases some form of interlock mechanism would be provided so that any machinery located within the access area cannot be operated whilst the machine guard is in the open or partially open position.

The guiding means may be provided by rails, rollers in tracks or other suitable expedient. Preferably the guiding means and the movable edges of the frames are enclosed or covered by a removable housing or enclosure.

A preferred embodiment of this invention will now be described, by way of example, with reference to the accompanying drawings wherein:

FIG. 1 is a front elevation of the exemplary machine guard shown in the closed position;

FIG. 1 a is a detail of one side of the guard as depicted in FIG. 1;

FIG. 2 is a side elevation of the guard shown in FIG.

FIG. 3 is a section on 3--3 of FIG. 1 but with the guard in the open position;

FIG. 4 is a section on 44 of FIG. 1;

FIG. 5 is a section on 5-5 of FIG. 1;

FIG.'6 is a section on 66 of FIG. 1;

FIG. 7 is a section on 7-7 of FIG. 1; and

FIG. 8 is a view in the direction of the arrow of FIG. 7.

The exemplary machine guard is arranged so that it may be mounted on, or supported on the ground adjacent a machine having a frontal access area. The machine guard is also arranged for vertical displacement relative to the machine. The machine is not depicted in the drawings.

The exemplary machine guard comprises a portal structure comprising a pair of side members 1, and a front member 2 secured thereto. The front member has an upper bridging element 3 and extends above the height of the side members 1. The upper extent of the bridging element 3 would be above the machine access area. The front member'Z also includes a pair of opposed vertical elements 4 on each of which is mounted a guide rail 5. Each of the guide rails 5 is enclosed by a cover 6 secured to the respective vertical element 4.

Three rectangular frames 7, 8 and 9, are mounted on the guide rails 5 for relative sliding movement. Each of the three frames 7, 8 and 9 have sleeved bosses 10, ll; 12, 13; and 14, 15 respectively at the lower and upper edges of their opposed sides. The three frames are of different sizes and are nested together so that they overlie or underlie each other as can be seen from FIGS. 3 and 4.

Each frame 7, 8 and 9 includes a guard panel 16, 17 and 18 respectively, each panel being of similar area and corresponding to about onethird of the machine access area to be opened and closed.

The inmost frame 9 comprises supporting elements on which the bosses 14 and 15 are mounted and the guard panel 18 of a 'meshed material extends across the area of the frame 9.

The intermediateframe 8 is approximately twice as long as the inmost frame 9 and has supporting elements on which the bosses 12 and 13 are mounted. The meshed guard panel 17 only extends across the upper portion of the frame 8 so that the lower portion is open.

The outmost frame 7 is approximately three times as long as the inmost frame and has supporting elements on which the bosses and 11 are mounted. In a similar manner as the intermediate frame 8, the meshed guard panel 16 only extends across the upper portion of the frame 7 so that the lower portion is open.

The driving rod 20 of a pneumatic cylinder 21 secured to a side member 1 is connected to the upper boss or the element supporting same of the inmost frame. The pneumatic cylinder would be coupled to an interlock system so that actuation was controlled in conjunction with the cycle or sequence of machine operation.

As will now be explained, the three frames may be displaced on actuation of the pneumatic cylinder. Normally, when the machine guard is closed, as depicted particularly in FIGS. 1 and 4, the three frames are lowered so that the. lower bosses rest on one another and the three respective guard panels 18, 17 and 16 extend adjacent one another to provide a continuous shutter. When the pneumatic cylinder is actuated to drive the rod upwardly, the inmost frame 7 is raised, and when the upper boss 15 thereof contacts the upper boss 13 of the intermediate frame, then that too is raised. Similarly, on further raising of the inmost frame the outmost frame is lifted so that eventually all of the frames are raised into the open position depicted in FIG. 3. In this position all of the guard panels are in overlying alignment and the machine access area is open and unobstructed as only the open lower portions of the intermediate and outmost frames are adjacent the access area.

As the frames are maintained in the open position by the extension of the driving rod 20, if there should be a failure in the pneumatic supply, then the machine guard will automatically return to the closed, lowered position.

Now it will be appreciated that a very compact arrangement may be achieved as the headroom required for the invented machine guard only corresponds to the length of one guard panel and the upper supports or mountings for the guide rails.

It is also envisaged that the machine guard may embody a safety leading edge arrangement. As is depicted in FIGS. 6 7 and 8 the inmost frame 7 has a lower transverse frame member 25 on which is mounted a leading edge in the form of a strip 26. The strip 26 is mounted on the member 25 by bolts 27 extending through slots 28 in the strip 26 so that the strip 26 may move relative to the member 25 if an obstruction is contacted when the inmost frame is lowered. The upper edge of the strip 26 engages with a roller arm 28 for actuating a micro switch or similar expedient in the control circuit or other control mechanism to prevent further lowering of the machine guard and, if required, to raise the machine guard. I

From the foregoing description it will be appreciated that the invention may be employed with two or more than three frames. Additionally, instead of the frames being displaced vertically, the arrangement could be modified so that the frames are moved horizontally to one side of the machine access area.

I claim:

, 1. In combination with a machine, a guard comprising a fixed portal structure defining an access opening and a plurality of frames movably mounted on said structure, said plurality of frames including a first frame in a first position slidably mounted on guide means on said structure for relative movement to a secend position, a second frame in a first position slidably mounted on said guide means for relative movement to a second position, a guard panel carried on said second frame, a guard panel carried on said first frame underlying said first mentioned guard panel so that said access openingis unobstructed by said guard panels, driving means mounted on said portal structure and connected to at least said first frame for moving said first and second frames to said second respective positions wherein said guard panels extend adjacent to each other to close said access opening, the arrangement of said frames being such that said first frame rests within said second frame with the length of said first frame in the direction of movement being substantially less than the length .of said second frame in the direction of movement, said first and said second frames each having first end abutments abutting in said first position, and said first and second frames each having second end abutments opposed to said first end abutments with said second end abutments-abutting when said guard is in said second position, said driving means being connected to said first frame, movement of said first frame from said second position to said first position being transmitted through said first end abutments.

2. A guard according to claim 1 wherein said guide means comprises a pair of parallel, spaced apart guides spanned by said first and second frames with their said respective guard panels, said guides defining opposed sides of said access opening and each extending at one end beyond said opening by a length corresponding substantially to at least the length of said guard panel of said first frame.

3. A guard according to claim 2 wherein each said frame is substantially rectangular, and each said guard panel is substantially rectangular the first-mentioned guard panel having an edge portion underlying an adjacent edge portion of said second-mentioned guard panel when said guard is in said second position with said first and second-mentioned guard panels being of substantially the same area.

cal sliding movement on said guides, and each end abutment comprises a sleeved boss engaging one of said rails for longitudinal sliding movement.

6. A guard according to claim 5 further comprising a third frame with a guard panel, in said first position said third frame and guard panel overlying said second frame and said second-mentioned guard panel. 

1. In combination with a machine, a guard comprising a fixed portal structure defining an access opening and a plurality of frames movably mounted on said structure, said plurality of frames including a first frame in a first position slidably mounted on guide means on said structure for relative movement to a second position, a second frame in a first position slidably mounted on said guide means for relative movement to a second position, a guard panel carried on said second frame, a guard panel carried on said first frame underlying said first mentioned guard panel so that said access opening is unobstructed by said guard panels, driving means mounted on said portal structure and connected to at least said first frame for moving said first and second frames to said second respective positions wherein said guard panels extend adjacent to each other to close said access opening, the arrangement of said frames being such that said first frame rests within said second frame with the length of said first frame in the direction of movement being substantially less than the length of said second frame in the direction of movement, said first and said second frames each having first end abutments abutting in said first position, and said first and second frames each having second end abutments opposed to said first end abutments with said second end abutments abutting when said guard is in said second position, said driving means being connected to said first frame, movement of said first frame from said second position to said first position being transmitted through said first end abutments.
 2. A guard according to claim 1 wherein said guide means comprises a pair of parallel, spaced apart guides spanned by said first and second frames with their said respective guard panels, said guides defining opposed sides of said access opening and each extending at one end beyond said opening by a length corresponding substantially to at least the length of said guard panel of said first frame.
 3. A guard according to claim 2 wherein each said frame is substantially rectangular, and each said guard panel is substantially rectangular the first-mentioned guard panel having an edge portion underlying an adjacent edge portion of said second-mentioned guard panel when said guard is in said second position with said first and second-mentioned guard panels being of substantially the same area.
 4. A guard according to claim 3 wherein said driving means comprises a pneumatic cylinder and a safety leading edge is provided on at least one edge portion of a frame, said safety leading edge being coupled to said driving means to actuate said guard on operative functioning of said safety leading edge.
 5. A guard according to claim 4 wherein said guides comprise rails supported on said portal structure and said first and second frames extend vertically for vertical sliding movement on said guides, and each end abutment comprises a sleeved boss engaging one of said rails for longitudinal sliding movement.
 6. A guard according to claim 5 further comprising a third frame with a guard panel, in said first position said third frame and guard panel overlying said second frame and said second-mentioned guard panel. 